Sheeting panels for trench shoring

ABSTRACT

A substantially rectangular trench shoring sheeting panel made primarily of polyethylene includes at least one pair of hand holes. In some embodiments, the sheeting panel includes a plurality of buttons protruding outwardly from one of the sheeting panel&#39;s surfaces. As compared to three-quarter inch FinnForm, the polyethylene sheeting panel typically has (i) equivalent or superior structural properties and (ii) a significantly lower useful-life cost.

CROSS-REFERENCE TO PRIORITY APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 61/508,154, filed Jul. 15, 2011, in the U.S.Patent and Trademark Office. This application incorporates the earlierprovisional application by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to the field of shoring systems forsupporting the sides of a trench or hole in the ground and, inparticular, sheeting panels for hydraulic shoring techniques.

Various shoring techniques have been employed for supporting the sidesof a trench or hole in the ground during excavation. One shoringtechnique, called “aluminum hydraulic shoring,” employs hydraulic jacks,aluminum shoring rails, and shoring sheeting panels to support the sidesof the trench. After a portion of the trench is excavated, two sheetingpanels may be placed substantially parallel to one another on oppositeside of the trench. The shoring rails, typically already connected bythe hydraulic jacks, are then placed on the faces of the two sheetingpanels. The hydraulic jacks extend perpendicularly from the face of onesheeting panel to the face of the second sheeting panel. After properplacement of the shoring rails and hydraulic jacks, the hydrauliccylinders within the jacks are pressurized. Alternatively, the hydraulicshoring rails may be fastened to the sheeting panels, and then theassembly of rails and panels may be placed in the trench.

In 1989, the Occupational Safety and Health Administration (OSHA)adopted federal standard 29 CFR 1926, Subpart-P establishing safetyrequirements for excavation work-sites. In particular, Regulation 1926,Subpart-P, Appendix D includes item (g)(7) identifying the types ofshore sheeting that may be used for aluminum hydraulic shoring fortrenches. Item (g)(7) states: “Plywood shall be 1.125 inch thicksoftwood or 0.75 inch thick, 14 ply, arctic white birch (Finland form).Please note that plywood is not intended as a structural member, butonly for prevention of local raveling (sloughing of the trench face)between shores.”

The OSHA Subpart P standard also requires (i) manufacturers of shoringequipment to develop their own tabulated data for the aluminum hydraulicshoring equipment they develop, and (ii) users of the equipment toadhere to the data developed for the shoring rails and sheeting panelsthey are using. To afford themselves of broader liability protection,most manufacturers of hydraulic shoring have tried to stay as close aspossible to the data developed by OSHA. Other types of sheeting such assteel plate and plywoods with performance equivalent to and even lessthan three-quarter-inch, 14 ply, Artic White Birch (Finland form or“Finnform”) have been allowed. Finnform plywood is a relativelydifficult standard to meet or exceed so it is used as the calibrationstandard within the industry.

To date, plywood has primarily been used for shoring sheeting panels.Although plywood performs well as a shoring panel, the material also hasa number of drawbacks. In particular, water, mud, and drying cause theplywood panels to gray and eventually delaminate. The handling andinstallation of plywood panels also breaks the corners of the plywoodpanels. Thus, the useful life of plywood sheeting panels isapproximately one to two years.

Additionally, plywood breaks and punctures relatively easily. If aplywood sheeting panel is punctured or an edge of the panel is broken,the overall area of restraint provided by the panel is reduced.Unrestrained areas of soil and rock may shift and move creatingpotential safety hazards.

As noted, plywood sheeting panels can be damaged during handling, whichmay include dragging the panel. Over time, the panel becomes bent in theface plane, and breaking and splintering occurs on the face of thepanel. As the deterioration progresses the coverage and effectiveness ofthe sheeting becomes less than intended. Furthermore, splintering on theedges and face of the plywood present a safety hazard to workershandling the shores (e.g., the assembly of shore rails and sheetingpanels). Even with gloves on, large plywood splinters can penetrate thehands and other parts of the body. Workers inside the trench that arenot handling the shores can still brush up against the shore receivingpuncture wounds. Working at the trench level exposes the upper body andhead to the surrounding shoring sheeting.

To combat these issues, metal edge protectors may be installed onplywood sheeting panels, and the shores may be cleaned and refurbishedafter each use. The cost and time associated with replacing the plywoodpanels, installing metal edge protectors, and cleaning the shores can beexcessive.

Therefore, a need exists for an improved sheeting panel that meets orexceeds the OSHA regulations for aluminum hydraulic shoring fortrenches. More particularly, there exists a need for a sheeting panelthat reduces the long-term cost of maintaining and installing shoringsystems and is durable, easy to handle and maintain, and safe for bothshore installers and workers inside the trench.

SUMMARY OF THE INVENTION

In one aspect, the present invention embraces a substantiallyrectangular trench shoring sheeting panel made primarily ofpolyethylene. The sheeting panel includes a front surface, a rearsurface, and four edges.

In an exemplary embodiment, the sheeting panel includes at least onepair of hand holes extending through the front surface and the rearsurface. Each of the hand holes is separated a lateral distance from theother along one of the sheeting panel's four edges.

In another exemplary embodiment, the sheeting panel includes four pairsof hand holes extending through its front surface and rear surface. Eachpair of hand holes is typically located along a different edge of thesheeting panel. Within each pair of hand holes, each hand hole isseparated a lateral distance from the other along one of the sheetingpanel's four edges.

In yet another exemplary embodiment, at least one side of the sheetingpanel includes buttons protruding outward from a majority of thesheeting panel's surface.

In yet another exemplary embodiment, a strip of area extending centrallyacross the length of the sheeting panel's surface is free of buttons.

In yet another exemplary embodiment, the sheeting panel includes fourcorner holes located in each of the shoring panel's corners.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages of the invention and themanner in which the same are accomplished will become clearer based onthe following detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is an anterior plan view of a sheeting panel in accordance withone embodiment of the invention; and

FIG. 2 is a posterior plan view of a sheeting panel in accordance withone embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described more fully hereinafter withreference to the accompanying drawings, in which multiple embodiments ofthe invention are shown. This invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art. Like numbersrefer to like elements throughout.

The present invention embraces a sheeting panel made primarily ofpolyethylene. As depicted in FIGS. 1 and 2, the sheeting panel 10 has asubstantially rectangular shape. The term “substantially rectangular” ismeant to succinctly describe a simple geometric shape approximating arectangle. In this regard, the sheeting panel 10 includes a frontsurface 11 (FIG. 1) and a rear surface 12 (FIG. 2). The terms “front”and “rear” are simply meant to distinguish the two sides of the sheetingpanel 10. In exemplary embodiments, the sheeting panel 10 isapproximately 44.5 inches wide, 96 inches long, and has a thickness ofapproximately half an inch.

The sheeting panel 10 typically includes four pairs of hand holes 14,15, 16, and 17 to facilitate safe handling. The hand holes 14, 15, 16,and 17 may be molded into the polyethylene sheeting panel 10 duringmanufacturing. Alternatively, the hand holes 14, 15, 16, and 17 may becut out of the sheeting panel 10. For a given pair of hand holes 14, 15,16, or 17, the hand holes are typically separated a lateral distancefrom each other (i.e., spaced apart) along one of the four edges of thesheeting panel.

As depicted in FIG. 1, a pair of hand holes 15 is located at the rightend of the sheeting panel 10. The left end of the sheeting panel 10includes a pair of hand holes 17. The top edge of the sheeting panel 10includes a pair of hand holes 14. Finally, a pair of hand holes 16 islocated at the bottom edge of the sheeting panel 10. The terms “right”and “left” are used simply to distinguish the two ends of the sheetingpanel. Similarly, the terms “top” and “bottom” are used to distinguishthe two lengthwise edges of the sheeting panel.

As noted, the sheeting panel typically includes pairs of hand holes.That said, the sheeting panel 10 may include individual hand holes. Forexample, if the width of the sheeting panel is relatively small, asingle hand hole may be sufficient to facilitate safe handling.

The sheeting panel 10 may also include four corner holes 31, 32, 33, and34. As depicted in FIG. 1, corner hole 31 is offset from the top edgeand right end of the sheeting panel 10. Corner holes 32, 33, and 34 aresimilarly offset from their respective edges and ends. Ropes or cablesmay be passed through the corner holes 31, 32, 33, and 34 to facilitateinstallation or removal of the sheeting panel 10. The corner holes 31,32, 33, and 34 may be molded into the polyethylene sheeting panel 10during manufacturing. Alternatively, the corner holes 31, 32, 33, and 34may be drilled or cut out of the sheeting panel 10.

As depicted in FIG. 2, at least one side of the sheeting panel 10typically includes a plurality of buttons (e.g., dimples). The buttons22 protrude outward from the rear surface 12 of the sheeting panel 10 toincrease the frictional force (i.e., provide extra traction) between theshore rails and the sheeting panel 10, thereby reducing the risk ofsliding or slipping. Typically, the plurality of buttons 22 is locatedon a majority of the sheeting panel's surface (e.g., between about 60and 90 percent of the sheeting panel's surface). In some embodiments, astrip of area extending centrally across the length of the sheetingpanel's surface is free of buttons (i.e., no buttons protrude from thepanel's surface in this area).

Alternatively, the side of the sheeting panel 10 facing the trench wallmay include buttons 22. In such an arrangement, the buttons 22 increasethe frictional force (i.e., provide extra traction) between the verticalface of the trench, thereby reducing the risk of sliding or slipping.

As previously noted, the sheeting panel is made primarily ofpolyethylene, which provides significant advantages in terms of bothconvenience and structural performance as compared to typical FinnFormplywood sheeting panels. The polyethylene sheeting panel may bemanufactured in a variety of colors (e.g., black or white), and iseasily cleaned by spray washing. Furthermore, the polyethylene sheetingpanels can be cut and drilled with the same tools that are used forplywood sheeting panels.

From a structural standpoint, the polyethylene sheeting panels provideadditional benefits. For example, the polyethylene sheeting panels donot splinter or delaminate on the panel-face or edges. Furthermore, thepolyethylene sheeting panels deflect rather than breaking when loadedexcessively. A 44.5-inch-wide, 96-inch-long, and half-inch-thickpolyethylene sheeting panel weighs approximately seventy-eight pounds.The polyethylene sheeting panels also meet or exceed the structuralproperties of three-quarter inch FinnForm.

Table 1 (below) is a comparison of physical and structural properties ofpolyethylene sheeting panels to the plywood panels allowed in OSHARegulation 1926, Subpart-P, Appendix D, item (g)(7).

TABLE 1 Ultimate Unit Maximum Bending Weight Bending Modulus of Momentof Section Thickness Strength per Moment Elasticity Inertia ModulusPanel (inch) (psi) (psf) (in-lb) (ksi) (in⁴) ks (in⁴) Polyethylene 0.56700 2.63 3350 304 0.125 0.500 FinnForm 0.75 6244 2.71 3465 1830 0.1830.555 Softwood 1.125 3300 3.30 2455 1800 0.27 0.744

Despite the fact that OSHA Regulation 1926 does not consider sheeting tobe a structural member, from an engineering standpoint, a structuralcomparison is an appropriate way to compare the panels. In a structuralsense, 1.125-inch-thick softwood is inferior to both polyethylenesheeting panels and FinnForm. Maximum bending moment is a particularlynotable value in Table 1 because, if a panel were to fail by trench wallcollapse, bending would be the failure mode of the sheeting. Althoughthe FinnForm panel has a higher maximum bending moment than thepolyethylene sheeting panel, the overall analysis indicates that thepolyethylene sheeting panel is technically equivalent to the FinnFormpanel.

The modulus of elasticity is much lower for polyethylene sheetingpanels. Although this indicates that the panel will deflect more whenloaded, for the purpose of preventing local raveling, it is consideredan advantage because it allows the shore and sheeting to conform to thetrench wall without breaking the sheeting. The higher modulus ofelasticity associated with plywood and FinnForm is an indication that itis more brittle and will break, delaminate, or puncture more easily. Acomplete structural analysis of the sheeting panels of Table 1 can befound in Appendix 1, wherein the polyethylene sheeting panel is referredto as the “SHOR-MAT Panel.”

Additional mechanical tests were performed on polyethylene sheetingpanels in accordance with some embodiments of the present invention. Theresults of those tests can be found in Appendix 2.

The polyethylene sheeting panel of the present invention alsofacilitates a reduction in the cost associated with maintaining andinstalling shoring equipment. In this regard, the following exemplarycost comparison between polyethylene sheeting panels and FinnFormsheeting panels demonstrates that the inventive sheeting panels canfacilitate a substantial cost savings.

EXAMPLE

The use of sheeting with hydraulic shoring applications is dependent ondepth of excavation and soil type. In general sheeting is required inexcavations over 10 feet deep in OSHA type B and C soils. The sheetingmay be attached to the shoring or set inside the excavation before theshore (i.e., the shore rails and hydraulic jack) is set and pressurized.Generally, on the West Coast and South Coast, sheeting is attached tothe shore, and, on the East Coast, it is set independently from theshore.

Shoring panels become damaged on the corners by rigging, dragging on thesurface during installation, and removal. Plywood also becomes bent andbroken due to raveled and uneven trench walls. Plywood is often cut tofit around pipes and other obstructions. Weather and ground water tableconditions also have an effect on the quantity of plywood used and thelife expectancy of the sheeting panels. Wet weather and coastal regionswill utilize more shoring sheeting than arid and central states. Thepurchase and installation of shoring sheeting panels is done at thelocal supplier level rather than at the manufacturer's level.

Table 2 (below) presents the summarized results of a cost estimate of auseful life cost comparison between polyethylene sheeting panels andFinnForm sheeting panels.

TABLE 2 Total Cost Material Cost Unit Cost per 100 sheets Panel (persheet) (per year) (over 10 years) FinnForm $90.00 $72.33 $72,327Polyethylene $180.00 $21.57 $21,572

In a major municipality on the West Coast a shoring supplier installs300 sheets of 4-foot×8-foot FinnForm on 150 hydraulic shores every twoyears. The useful life of the FinnForm sheeting is two years. Thetypical soils that the sheeting is used in are either coarse sands andgravels or medium stiff sandy clays. Rainfall is heavy in the winter andwater tables are high, within 8 feet of the surface.

The useful life of polyethylene sheeting panels is assumed to be over 10years. This useful life assumption is supported by experience usingpolyethylene materials in other harsher construction applications. Thecost of polyethylene sheeting panels is double (i.e., 2×) the cost ofFinnForm. The analysis includes the cost of purchasing the panels,installing them on the shores, removing the panels from the shores anddisposing of the dilapidated sheeting, and maintaining the shores aftereach use. Labor cost is assumed to be from the shoring supplier'sgeneral warehouse and yard maintenance workforce.

As shown in Table 2, the cost of operating and maintaining a trenchshoring operation can be significantly reduced by using the polyethylenesheeting panels of the present invention. The complete cost analysisused to generate Table 2 can be found in Appendix 3, wherein thepolyethylene sheeting panel is referred to as the “SHOR-MAT Panel.”

In the drawings and specification, there have been disclosed typicalembodiments on the invention and, although specific terms have beenemployed, they have been used in a generic and descriptive sense onlyand not for purposes of limitation, the scope of the invention being setforth in the following claims.

1. A trench shoring sheeting panel, comprising: a substantiallyrectangular sheeting panel made primarily of polyethylene, said sheetingpanel having a front surface, a rear surface, and four edges; and atleast one pair of hand holes extending through said front surface andsaid rear surface, each of said hand holes being separated a lateraldistance from each other along one of said sheeting panel's four edges.2. A trench shoring sheeting panel according to claim 1, wherein saidsheeting panel is made primarily of polyethylene having a modulus ofelasticity of less than 1000 ksi.
 3. A trench shoring sheeting panelaccording to claim 1, comprising four pairs of hand holes extendingthrough said front surface and said rear surface, wherein: each of saidpairs of hand holes is located along a different edge of said sheetingpanel than each of said other pairs of hand holes; and within each ofsaid pairs of hand holes, each of said hand holes is separated a lateraldistance from the other along one of said sheeting panel's four edges.4. A trench shoring sheeting panel according to claim 1, comprisingbuttons on at least one of said sheeting panel's surfaces, said buttonsprotruding outward from a majority of said sheeting panel's surface. 5.A trench shoring sheeting panel according to claim 4, wherein a strip ofarea extending centrally across the length of said sheeting panel'ssurface is free of buttons.
 6. A trench shoring sheeting panel accordingto claim 1, comprising four corner holes extending through said frontsurface and said rear surface, wherein said corner holes are located ineach of the shoring panel's corners.
 7. A trench shoring sheeting panel,comprising: a substantially rectangular sheeting panel made primarily ofpolyethylene, said sheeting panel having a front surface, a rearsurface, and four edges; and four pairs of hand holes extending throughsaid front surface and said rear surface, each of said hand holeslocated along a different edge of said sheeting panel than each of saidother pairs of hand holes; and buttons on at least one of said sheetingpanel's surfaces, said buttons protruding outward from a majority ofsaid sheeting panel's surface; wherein each of said pairs of hand holesis separated a lateral distance from the other along one of saidsheeting panel's four edges.